Krško containment vent installed

04 March 2014

Westinghouse has completed the installation of a passive containment filtered venting system (CFVS) at the Krško nuclear power plant in Slovenia.

Krško (Image: NEK)

The newly-installed CFVS consists of five aerosol filters inside the containment building, and an iodine filter and various auxiliary components (including rupture disks) inside the auxiliary building. In the event of a severe containment over-pressurisation, such as happened in the March 2011 accident at Japan's Fukushima Daiichi plant, the CFVS would allow depressurisation to occur while minimizing the radioactivity released into the environment. During depressurisation, the metal fibre aerosol filters would retain airborne radioactive aerosols; and radioactive iodine and its organic compounds would be retained by the iodine filter – a molecular sieve doped with zeolite – where the iodine combines with silver bound to the zeolite.

This so-called dry filter method (DFM) was developed by filter and heating, ventilation and air conditioning supplier YIT Germany (now Krantz) for the backfit of German nuclear power plants after the Chernobyl accident in 1986. The Krško CFVS was developed by Westinghouse in partnership with Krantz, a German subsidiary of Finland's Caverion Group, which was spun out of YIT Group last year.

The design and installation was completed in 15 months, following the award by operator Nuklearna Elektrarna Krško (NEK) of two contracts in November 2012 for the venting system and a passive autocatalytic recombiner hydrogen-control system. The two severe accident management systems were required by the Slovenian nuclear regulator as a result of stress tests carried out in response to the Fukushima accident. Installation of the hydrogen recombiner was completed in October 2013.

Construction of the 696 MWe Westinghouse PWR at Krško – the first western nuclear power plant in eastern Europe – commenced in 1975 and it was connected to the grid in 1981. The plant was built as a joint venture between Slovenia and Croatia, which were both part of Yugoslavia at the time. Croatian state-owned company Hrvatska Elektroprivreda and Slovenian state-owned company Gen-Energija co-own NEK. The reactor is currently due to shut down in 2023, but NEK has applied for a 20-year extension to the operating lifetime.